The present invention pertains to an improved device for use on a sewing machine to automatically orient a chain of stitches and hold the same in a position forward of the presser foot so that said chain will be sewn into the seam to be formed on the next piece of material to be stitched.
As is well known, sewing machines that are adapted to form seams on a succession of pieces of material such for example as stitches of Classes 400, 500, 600, etc. according to the classification of the Federal Standard Catalog (U.S.A.), the stitches continue to be formed in the area between successive pieces of material, and means are provided for detaching said pieces one from the other by an automatic chain cutting device after the pieces have been caused to be advanced beyond the presser foot of the machine.
U.S. patent application Ser. No. 872,973 filed Jan. 27, 1978 now U.S. Pat. No. 4,149,478 discloses an automatic device for locating and holding a chain of stitches to be incorporated into the initial stitches of the seam to be formed on the next workpiece. This device includes an orienting element that serves to remove the cut chain from the cutting device and by means of a cooperating clamping and intake device the chain is then positioned and held in a plane which coincides substantially with the sewing axis and is in readiness for incorporation into the next seam to be formed. With the use of devices of this type, it has been possible to eliminate some of the disadvantages encountered with the devices noted above which, for example, include unsatisfactory insertion of the chain into the seam being formed, and the non-uniform thickness of the stitch in the initial portion of the new seam.
As is known, the chain of stitches is cut only if it is attached to a work piece which is caused to be advanced in front of the chain cutting device, because otherwise said chain assumes a position parallel to the cutting element itself of said device.
Therefore the length of the chain to be incorporated in a new seam depends on the amount of time which the machine requires to effectively stop after forming the last stitch on the sewn piece and the cutting of the chain from said piece.
Thus, lengths frequently result which are, excessively long, and thus the chain, being held only by the mechanical clamp that is located at a predetermined and fixed position spaced from the stitching instrumentalities of the machine, can be of a length which will interfere with the desired manner of its being incorporated into the seam.
The improved device according to the present invention provides a combined positioning, clamping and cutting apparatus that is effective, in addition to locating the chain, in cutting the same so as to selectively control the length which will be incorporated into a seam of stitches.
Additionally, the apparatus of the invention is movably mounted on a sewing machine so that there is no possibility of interference with the workpieces during their movement on the work surface of said machine.